Anyone use a Watts 80 ballcock thermal expansion valve?

As an alternative to an expansion tank the Watts 80 is recommended for pressure relief when connected to a closed system (county or city water). Anyone use one? Do they work and how reliable are they? Thank you.

FWIW, a properly operating expansion tank does not waste water, a pressure relief valve will. An ET helps to maintain a more even pressure, an relief valve only puts a top limit on it, not hold it to a more proper level. A relief valve may be a good backup, but they can fail as can an ET, then you have nothing to prevent overpressure and potential leaks. Personally, I would not use one as my primary closed system solution.

There a very old, shop worn saying, "If is ain't broke, don't fix it". I think that applies very well to this question. A thermal expansion tank works very well, does not waste water, is easily replaces when it fails, and is inexpensive. Why go look for an alternative?

I see your points, all of them... I'm looking at an Amtrol ST-5 2 gallon, looks good because I really wanted a lined tank, for corrosion reasons. If anyone knows of a better one, Please let me know. Thank you. By the way is there a certain distance it has to be installed from the hot water heater? I'd like it to be in my outside pump room just after the pressure regulator.

It can be installed anywhere on the cold supply side after the PRV. But, there should be no shutoff valve between the WH and the new expansion tank. This is to ensure it can do its thing when the WH starts to run. They don't last forever, but do last a number of years. Adjust the precharge to your static water pressure before installation.